1. Field of the Invention
The present invention relates to a bearing cap for a main bearing in an internal combustion engine. The cap consisting partially of an aluminum alloy and partially of an iron alloy forming a core in the aluminum material. The core has lateral portions with bores for mounting bolts and a central portion between the lateral portions. The central portion terminates at a distance from a supporting surface for a bearing shell, the supporting surface being the outer limiting surface of an aluminum alloy layer outside the iron core.
2. Background Information
It is known in the art to use main bearing caps made entirely of aluminum in aluminum engine blocks to provide a design which is as light as possible. The lowest possible weight can, however, only be achieved at the cost of increased mechanical engine noise due to the greater thermal expansion of the aluminum material causing in increased bearing clearance. It is also known to combine low weight with reduced noise by casting an iron core in the aluminum material, so that the thermal expansion resulting in increased bearing clearance is less than in a bearing cap made entirely of aluminum. In a previously known design of the type described above by way of introduction and disclosed in U.S. Pat. No. 5,203,854, the iron alloy core has a channel running through the middle of the central portion. This channel is filled with the aluminum alloy forming a coherent mass with the aluminum alloy to provide a mechanical grip between the core and the aluminum material. This channel weakens the core in its most loaded section, while the aluminum alloy in it, due to the higher thermal expansion of the aluminum alloy compared with the iron alloy, causes higher bearing distortion in the most loaded section.